The tweet included no commentary, so it may simply be Ayer sharing art he likes - or it could be a cryptic tease of the film's villain. Born Roman Sionis, Black Mask is a ruthless gangster with a sadistic streak.

Details about the project are scarce, but it will involve Harley Quinn teaming up with Catwoman and Poison Ivy, as in the comic book version of Gotham City Sirens.